Have him get a regular manicure and pedicure (nails clear coat, toes colored) to remind him that sissy girls need to take care of their nails
This is great humiliation as it will remind him both public and private that he's a sissy every time he looks at his fingernails or toenails. It will also force him to take better care of himself and improve his personal care and hygiene habits.
Remind him that a sissy needs to have her nails and toes in perfect condition always and force him to make an appointment for a manicure and pedicure at the nearest salon. Explain to him that you expect him to go to the salon at least once every two weeks. Conduct regular surprise inspections of his hands and toes, and if they are dirty or not perfectly manicured, then punish him by making him paint them pink for 1 day. If he is caught again, make the punishment for 2 days, and so on and so on. If you are forcing him to get a color, accompany him to the salon and tell the woman giving the manicure which color he must have.
Have him make the appointment at the salon on one of the days of the week he's required to wear a bra. A summer approaches and it gets hotter, he will have trouble justifying wearing a sweater to the salon and eventually he'll be forced to wear just a shirt where his bra will be potentially visible.
He should always have well manicured nails, and you should inspect them by surprise whenever he doesn't expect it. Enforce the punishment of colored nails at least once from the very beginning, so that he will not challenge you as he knows you are serious en enforcing this on a regular basis. you can expect him to get a manicure as often as you do.
Since most nail salons are full of women, you can use this occasion to play with him and publically humiliate him a little. Make sure the woman in charge of the salon knows you are in charge of the relationship and you make the decisions about the color of nails you want. You can have her tease him by telling him that if she sees his nails in such bad condition next time, she'll have to paint them pink as you instructed her too.
This will only be effective if you show you are serious and conduct regular and consistent surprise inspections and strictly enforce painting his nails pink for one day the first time you notice the slightest imperfection (which should be fast). It will keep him constantly worried about keeping clean and perfect, as after the first colored painting, he won't want that humiliation again.